20hp no reverse

[Jake N]

Ok, my same 20 hp Mercury that I just bought that is running rough just lost reverse gear.

I was running it in a tub when I revved the motor up, it fell in gear and I shut it off. Immediately thereafter, I determined that it would not go in reverse.

I know the reverse gear worked before, I have already tried it. The previous owner just had the foot off to replace the impeller, so I'm wondering if he didn't put it together wrong.

I looked for some sort of interlock for reverse in the powerhead compartment but could not find one.

I'm suprised that I couldn't find some sort of safety device in the tiller that blocks the reverse gear.

Ideas?

 

[Motor Boater Bill]

Re: 20hp no reverse

There is an interlock between the throttle and shifter: In neutral you can't turn the twist grip on the tiller handle much above idle. In reverse you can speed it up but not as much as in forward. That interlock is in the linkage at the bottom of the vertical throttle linkage shaft, below and to the right of the carb. If you have the throttle advanced too much I don't think you will be able to shift it into reverse.

Can you move the shifter handle?

 

[Motor Boater Bill]

Re: 20hp no reverse

Also, if the motor is not running, you need to turn the prop or the motor to shift into reverse--the clutch dogs are ramped and spring loaded for forward, they are square for reverse and if not aligned, they won't go. Try turning the prop shaft as you shift into reverse. Don't keep turning it after it goes into gear. Pull the rope to confirm the prop now turns in reverse.

And, you have probably found that the motor tilt locks down in reverse and neutral, and the lockdown clamp releases in forward.

 

[Jake N]

Re: 20hp no reverse

Can you move the shifter handle?

Yes, into forward but not reverse.

 

[Jake N]

Re: 20hp no reverse

Also, if the motor is not running, you need to turn the prop or the motor to shift into reverse--the clutch dogs are ramped and spring loaded for forward, they are square for reverse and if not aligned, they won't go. Try turning the prop shaft as you shift into reverse. Don't keep turning it after it goes into gear. Pull the rope to confirm the prop now turns in reverse.

And, you have probably found that the motor tilt locks down in reverse and neutral, and the lockdown clamp releases in forward.

I've tried turning the prop while pressing on the shifter, but no luck.

Actually, I had not noticed the lockdown clamp feature. Interesting.

 

[Motor Boater Bill]

Re: 20hp no reverse

When it "fell in gear" did it go into fwd or rev?

If the shift linkage is not lined up properly when the lower unit is replaced, the indent on the shift handle can be off and make it more prone to "falling into gear" which is usually fwd. You could drop the LU and see if you can shift it with it off the motor, and see how the linkage feels without the lu in place. Then put both in neutral and reassemble.

That still doesn't expain why it won't go into reverse when it did before. But you'll know more if you drop the lu.

Do you have a manual? I'd recommend you not jump into this without one.

 

[Jake N]

Re: 20hp no reverse

When it "fell in gear" did it go into fwd or rev?

If the shift linkage is not lined up properly when the lower unit is replaced, the indent on the shift handle can be off and make it more prone to "falling into gear" which is usually fwd. You could drop the LU and see if you can shift it with it off the motor, and see how the linkage feels without the lu in place. Then put both in neutral and reassemble.

That still doesn't expain why it won't go into reverse when it did before. But you'll know more if you drop the lu.

Do you have a manual? I'd recommend you not jump into this without one.

It fell into forward.

I have a manual.

I watched the previous owner as he was troubleshooting the water pump. He was trying to attach the lower unit while the motor was in neutral. I left and when I came back he had it put together. After reading my manual I see that you are supposed to attach the lower unit while the motor is in forward. I suspect that this may be the problem. But he may have figured that out and finally attached the unit in forward, I don't know.

 

[Laddies]

Re: 20hp no reverse

Jake, if it has no neutral it probably broke the clutch dog when it jumped into gear a real common problem, FWD is spring loaded so it goes into FWD as defalt. Pull the drain plug and ck for pieces, I'm sure you will find some if so you will have to pull the carrier and clean then get a new clutch dog, non't run it much as pieces will damage brgs.

 

[Jake N]

Re: 20hp no reverse

Jake, if it has no neutral it probably broke the clutch dog when it jumped into gear a real common problem, FWD is spring loaded so it goes into FWD as defalt. Pull the drain plug and ck for pieces, I'm sure you will find some if so you will have to pull the carrier and clean then get a new clutch dog, non't run it much as pieces will damage brgs.

It has neutral, it does not go into reverse. I'll check the oil this afternoon when I get home. Tomorrow I'll get the chance to water test it again.

So nobody thinks that the lower unit was attached incorrectly and that reattaching it in the correct manner would solve my problems?

You can't blame me for wishing.

 

[Laddies]

Re: 20hp no reverse

Then the problem is linkage the rev lock cam or a missing tilt pin or the shift rod has jumped a spine

 

[Jake N]

Re: 20hp no reverse

Then the problem is linkage the rev lock cam or a missing tilt pin or the shift rod has jumped a spine

If the tilt pin is removed the motor will not go into reverse? Is the tilt pin is the 6 - 8" stainless pin that controls the tilt of the motor? (I know that sounds obvious.) My "tilt pin" is sitting next to my gas can. I don't know why it was removed, but it was removed lately (possibly a friend just messing with it.)

Sounds like you may have found the solution. Thanks!

 

[Jake N]

Re: 20hp no reverse

Then the problem is linkage the rev lock cam or a missing tilt pin or the shift rod has jumped a spine

If the tilt pin is removed the motor will not go into reverse? Is the tilt pin is the 6 - 8" stainless pin that controls the tilt of the motor? (I know that sounds obvious.) My "tilt pin" is sitting next to my gas can. I don't know why it was removed, but it was removed lately (possibly a friend just messing with it.)

Sounds like you may have found the solution. Thanks!

I don't know what is up with the pirate heads. I didn't mean to put them there.

 

[Laddies]

Re: 20hp no reverse

Thats probably the trouble Jake

 

[Motor Boater Bill]

Re: 20hp no reverse

Hey Bob--are you saying it won't go into rev without the tilt pin in place? I never knew that! Thanks for the info.

 

[Laddies]

Re: 20hp no reverse

Bill, The lock pawls get stuck on the transom and they won.t let it shift, They act just like the older engines with a bad shift cam or bent locking pawls--Bob